Tail lights not turning on, headlights not turning off...

I will preface that I know there are lots of other threads about stuff like this out there and I promise I have been reading through old threads to try not to double up...but electrical stuff is just SO much fun and I'm hoping maybe someone out there has some guidance that will save me some hours of searching.

So a few days ago I left work in the dark, hopped in the truck, start it, flip the headlights on, drive home. Getting home I'm backing up to a wall and noticed my tail lights are off, but brake lights are working...signals are working too. Huh maybe the bulbs died. I shut the car off and flip the lights switch to turn my headlights off...headlights don't turn off. Now I'm scratching my head like wtf is going on. So here is my best break down haha:

Truck off - all lights off
Turn truck on - all lights still off, signals, break, reverse lights work
Flip light switch - head lights turn on, all normal dash lights come on, tail lights do not
Flip light switch again (off) - main head lights stay on, corner head lights + dash lights turn off
Brights turn on/off/flash like normal
Turn car off + light switch off - headlights stay on, all others turn off
Disconnect battery to get headlights to turn off - back to square one

NOTE: I do have projector headlights (TRS - installed 2+ years ago and have been fine since)

I've pulled/checked + plugged back in all related fuses, pulled + plugged back in all headlight/tail light wiring connectors, seems like the light switch itself is still working...? (bc the dash lights turn on and off)...What can I check next? Where should I test with a multimeter? Anyone have something like this happen before and have a possible fix?

 

Do you have daytime running lights?

 

no, just the standard off, on & brights

 

I'd pull the plastic cover piece under the cluster/steering wheel (the one directly in front of your knees) and, and the steering column covers, and poke around make sure there's no clear issues with the wiring there. I had some weird headlight and wiper issues and once I got down there and looked the problem became obvious. I had the wires coming out of the steering column come loose where they hit the connector for the body harness.

Hope its that easy, otherwise its time to just start tracing wires end to end and testing with the multimeter. Something must be crossed or shorting somewhere

 

Did you try pulling any relays. If the headlight have one and it could be sticking closed. Might check those. Could also check the outputs on the headlight switch with a multi meter.
Being that head lights are staying on and tail lights aren't coming on I'd say there's an issue with the switch

 

Disconnect the headlights and see if anything changes.

 

dang, i know you dont want to hear this, especially after of 2yrs of no issues......

i would try swapping out the TRS lamps for conventional bulb housings(at least one)and then check the issues and see if this weirdness changes

that would rule out the TRS lamps

 

When this happens.
What happens if you flash the lights?

Like when you pull back in the switch.....

 

The ECM supplies a ground to the Head Relay.
You either have something back feeding the headlights.
Or the ECM isn't cutting the ground signal.
Or you have a something providing a ground to the relay other than the ECM.

I'd be looking for a ground on the R/W wire or pin 3 of the Head Relay.

 

pulling back functions normally flashing the brights.

I also noticed when I flip the light switch on and off the small corner head lights will turn on and off normally...the plot thickens

 

tried this, no changes with them disconnected. plugged everything back in after and now headlights turn on/off with the light switch...no idea what changed this time...not gonna say anything except s/o Clearwater Bill let's hope it sticks

Thanks all for the ideas so far, gonna get under the dash this weekend when I have some time

EDIT: jinxed myself. headlights read this comment and said oh nvm we're staying on

 

Hmmm

what type of bulbs in tails?